Yoke removal from a bonded yoke-cathode ray tube assembly

ABSTRACT

In a cathode ray tube-deflection yoke combination wherein the yoke is bonded to the cathode ray tube by a hot melt adhesive to effect semi-permanent adherance thereto, means for softening the adhesive to permit yoke removal for repair or replacement are provided. The adhesive softening means comprises resistance wire wound about the supporting posts which are surrounded by hardened adhesive in order to mount the yoke. Applying electrical current to the resistance wire softens the adhesive and allows the yoke to be removed.

United States Patent [191 Aldrich et al.

[111 3,831,123 [451 Aug. 20, 1974 YOKE REMOVAL FROM A BONDED YOKE-CATHODE RAY TUBE ASSEMBLY [75] Inventors: Floyd E. Aldrich, Waterloo; Joseph L. Hallett, Seneca Falls, both of NY.

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

22 Filed: Oct. 31, 1973 21 Appl.No.:411,303

52 us. on 335/210, 335/213, 178/7.8, 51 met ..n01r7 00 58 Field ofSearch ..335/210,212,213,313/75 [56] References Cited UNITED STATES PATENTS Brown 335/210 3.746.740 l()/I)73 Deal .335/2IOX Primary Examiner--G. Harris Attorney, Agent, or Firm-Norman J. OMalley; William H. McNeil]; Cyril A. Krenzer [57] ABSTRACT In a cathode ray tube-deflection yoke combination wherein the yoke is bonded to the cathode ray tube by a hot melt adhesive to effect semi-permanent adherance thereto, means for softening the adhesive to permit yoke removal for repair or replacement are provided. The adhesive softening means comprises resistance wire wound about the supporting posts which are surrounded by hardened adhesive in order to mount the yoke. Applying electrical current to the resistance wire softens the adhesive and allows the yoke to be removed.

3 Claims; 3 Drawing Figures BACKGROUND OF THE INVENTION This invention relates generally to cathode ray tubedeflection yoke combinations and particularly to such combinations wherein the deflection yoke is semipermanently bonded in operable position on the cathode ray tube. Still more particularly, the invention relates to means permanently mounted with the yoke for effecting removal thereof for repair or replacement. Deflection yokes are employed with cathode ray tubes in order to deflect an electron beam in a predetermined manner across the phosphor screen of the cathode ray tube. In the past it has been the practice to mount the deflection yoke within the television receiver by means of a complex jig arrangement which allowed the yoke to be moved in at least three directions in order to center the beam in an appropriate manner. Recently it has become the practice to adjust the yoke at the cathode ray tube manufacturing plant and then semipermanently bond the yoke in a fixed position on the tube by means of a hardenable adhesive. It is with the latter form of yoke mounting that this invention is concerned. Although the yoke is mounted upon the tube in a semi-permanent manner so that after mounting no positioning adjustments are possible, it nevertheless remains a fact that occasionally it will become necessary to remove a yoke from a cathode ray tube in order to replace or repair either the yoke itself or the tube. Under the present bonding techniques this has been an extremely difficult and dangerous procedure usually necessitating several sawing or pulling operations which usually destroyed the yoke and could frequently destroy the tube by breaking the glass envelope thereof. This always presents a dangerous situation since the cathode ray tubeis under ahigh vacuum and ,anycrackingor breakage ofthe glass wall will generally result in the tube imploding.

It is believed tobe an advance in the art if a means could be found for obviating the above difficulties.

OBJECTS AND SUMMARY OF THEINVENTION It is, therefore, an object of this invention to obviate the disadvantages of the prior art.

It is another object of the invention .to enhance the removal of semi-permanently mounted deflection yokes from cathode ray tubes without damage to either.

It is a further object of the invention to provide such means which are permanently affixed in the yoke mounting.

These objects are accomplished in one aspect of the invention by the provision of a yoke assembly which comprises an annular tube ring which surrounds the neck of a cathode ray tube and is bonded to the rear wall of the tube. The tube ring has at least one outer surface which carries a plurality of spaced apart projecting hollow studs extending rearwardly thereof. An annular yoke retainer ring which carries and supports a deflection yoke has an outer wall provided with a plurality of hollow pockets, one for receiving each of the projecting studs. A hardened thermoplastic adhesive substantially fills each of the hollow pockets and surrounds the studs which have been mounted therewithin, whereby the yoke retainer ring position is maintained. To effect removal,.an adhesive softening means is permanently associated with the hardened adhesive within the hollow pockets for softening the same whereby the yoke retainer ring and the yoke contained therein can be removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a prior art yoke mounting arrangement;

FIG. 2 is a partial sectional view illustrating the invention; and

FIG. 3 is a diagrammatic wiring diagram of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

Referring now to the drawings with greater particularity there is shown in FIG. 1 an exploded perspective view of a yoke and yoke mounting arrangement. The yoke mounting arrangement 10 comprises an annular tube ring 12 which is sealed to the rear wall of a cathode ray tube. The tube ring 12 is substantially symmetrically located and surrounds the cylindrical neck of the tube. Tube ring 12 is provided with an outer surface 14 and an inner hollow surface 16. The inner surface 16 is provided with an adhesive groove 18 which extends circumferentially about the interior 16. Outer surface 14 is provided with a plurality of hollow studs 20. In this instance, there are four studs 20. The hollow interior of each of the studs 20 communicates with the adhesive groove 18 so that adhesive can be injected into the hollowed inner surface 16. That is, during mounting of the tube ring 12 it is positioned in its desired location upon the rear wall of a cathoderay tube and is held, as by a jig arrangement, in that desired position. Liquid adhesive is then forced through the hollows in studs 20 under sufficient pressure to cause the liquid adhesive to flow about the interior of tube ring 12. After the adhesive has hardened or while the jig holding tube ring 12 in position is still in place, a plurality of sponge washers 22 are fitted over the hollow studs 20, one washer to each stud. Thereafter, the yoke mounting takes place.

The deflection yoke 24 comprises a ferro-magnetic core having a plurality of toroidal windings thereabout. One of the windings is partially indicated at 26. The core 24 is also provided with a front crown 28 which has a plurality of tabs 30 thereon and extending outwardly and rearwardly therefrom. The yoke 24 is inserted into a yoke retainer ring 32. The yoke retainer ring 32 comprises a circumferential wall having a plurality of spaced hollow pockets 34 provided thereon. The hollow pockets 34 are spaced in the same manner and in the same number as the hollow studs 20 on the annular tube ring 12. Pockets 34 have an open bottom and one side and a closed top having an opening 36 therein. The tabs 30 on front crown 28 of the yoke engage at least one of the walls of. each of the hollow pockets 34 to maintain the yoke position. With the yoke 24 mounted in the yoke retainer ring 32 the yoke retainer ring is positioned in a jig over the hollow studs 20. That is, the hollow studs 20 project into the hollow pockets 34 of the yoke retainer ring 32. The yoke and yoke retainer ring are held in a jig that is adjustable in both an X, Y, and Z direction. The bottom or tube facing openings of hollow pockets 34 are seated against and sealed by the sponge washers 22. After the optimum position of the yoke is determined, it is held by the jig in that optimum position and adhesive in liquid form is forced through the adhesive fill openings 36 in the top of pockets 34 in an amount sufficient to surround and bond to the hollow studs 20. When the adhesive has hardened the jig can be removed and the yoke is then permanently mounted in its desired position.

The yoke mounting arrangement described above provides a rigid and substantially permanent mounting of the yoke. In those cases where it becomes necessary to remove the yoke the process is extremely difficult.

Referring now to FIG. 2 the invention for obviating the above disadvantages will be described. Herein the yoke is shown mounted upon the neck portion 40 of a cathode ray tube 42. The tube 42 is shown only partially. It will be seen that surrounding the studs is an adhesive softening means 44 which in this instance is shown as being a resistance wire coil 46. The ends of the resistance wire 46 project outwardly from the bottom of sponge washer 22. The hardened adhesive is shown at 48 in cross-section. The softening means 44 are to be included or associated with each of the studs 20 although only one is shown in FIG. 2. The electrical connection between the coils can be a series one as shown in FIG. 3 wherein four resistance wire coils 46 are shown. By connecting an electrical supply to the terminals 50 of the softening means the adhesive 48 will be softened sufficiently so that the yoke and yoke retaining ring can be easily removed.

When nine inches of nichrome wire having a diameter of about 0.027 inch is employed for each coil 46, a six volt battery placed across the coil will result in a current flow of about 6 amperes. This power will generate enough heat within the coilto soften the adhesive.

The utilization of the softening means as a permanent feature of the yoke mounting assures removal of the yoke should this circumstance become necessary. The wires of the coils of the softening means in no way interfere with the operation of the yoke; and the terminals therefor can be provided upon any convenient location on the yoke.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

l. A deflection yoke assembly in combination with a cathode ray tube, said yoke assembly being fixed in position on said cathode ray tube, said yoke assembly comprising: an annular tube ring surrounding the neck of said tube and bonded to the rear wall of said tube, said tube ring having at least one outer surface carrying a plurality of projecting, hollow, studs extending rearwardly thereof; an annular yoke retainer ring supporting a deflection yoke, said yoke retainer ring having an outer wall provided with a plurality of hollow pockets, one for receiving each of said projecting studs; a hardened, thermoplastic adhesive substantially filling said pockets and surrounding said studs whereby said yoke retainer ring position is maintained; and an adhesive softening means permanently associated with said hardened adhesive for softening the same whereby said yoke retainer ring and the yoke contained therein can be removed.

2. The assembly of claim 1 wherein said softening means comprises: a coil of resistance heating wire surrounding each of said studs.

3. The assembly of claim 2 wherein said coils are electrically connected together and are provided with a common terminal. 

1. A deflection yoke assembly in combination with a cathode ray tube, said yoke assembly being fixed in position on said cathode ray tube, said yoke assembly comprising: an annular tube ring surrounding the neck of said tube and bonded to the rear wall of said tube, said tube ring having at least one outer surface carrying a plurality of projecting, hollow, studs extending rearwardly thereof; an annular yoke retainer ring supporting a deflection yoke, said yoke retainer ring having an outer wall provided with a plurality of hollow pockets, one for receiving each of said projecting studs; a hardened, thermoplastic adhesive substantially filling said pockets and surrounding said studs whereby said yoke retainer ring position is maintained; and an adhesive softening means permanently associated with said hardened adhesive for softening the same whereby said yoke retainer ring and the yoke contained therein can be removed.
 2. The assembly of claim 1 wherein said softening means comprises: a coil of resistance heating wire surrounding each of said studs.
 3. The assembly of claim 2 wherein said coils are electrically connected together and are provided with a common terminal. 